Pope Leo III was the head of the Roman Catholic Church from 795 to 816 AD. He is best known for crowning Charlemagne, the King of the Franks, as Emperor of the Romans in 800 AD, which marked the revival of the title in Western Europe. This event symbolized the alliance between the papacy and the Frankish kingdom, strengthening both religious and political authority. During his papacy, Leo III faced significant challenges, including opposition from local nobles in Rome. He was accused of various crimes and was temporarily exiled but later returned to power with the help of Charlemagne. His reign contributed to the establishment of the Holy Roman Empire and the influence of the papacy in European politics.